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ubifs: store cookie in private data

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Store the cookie to detect concurrent seeks on directories in
file->private_data.

Link: https://lore.kernel.org/r/20240830-vfs-file-f_version-v1-17-6d3e4816aa7b@kernel.org
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Christian Brauner <brauner@kernel.org>
This commit is contained in:
Christian Brauner 2024-08-30 15:04:58 +02:00
parent 0bea8287df
commit 1146e5a69e
No known key found for this signature in database
GPG Key ID: 91C61BC06578DCA2
1 changed files with 46 additions and 18 deletions
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64
fs/ubifs/dir.c
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@ -555,6 +555,11 @@ static unsigned int vfs_dent_type(uint8_t type)
return 0;
}
struct ubifs_dir_data {
struct ubifs_dent_node *dent;
u64 cookie;
};
/*
* The classical Unix view for directory is that it is a linear array of
* (name, inode number) entries. Linux/VFS assumes this model as well.
@ -582,6 +587,7 @@ static int ubifs_readdir(struct file *file, struct dir_context *ctx)
struct inode *dir = file_inode(file);
struct ubifs_info *c = dir->i_sb->s_fs_info;
bool encrypted = IS_ENCRYPTED(dir);
struct ubifs_dir_data *data = file->private_data;
dbg_gen("dir ino %lu, f_pos %#llx", dir->i_ino, ctx->pos);
@ -604,27 +610,27 @@ static int ubifs_readdir(struct file *file, struct dir_context *ctx)
fstr_real_len = fstr.len;
}
if (file->f_version == 0) {
if (data->cookie == 0) {
/*
* The file was seek'ed, which means that @file->private_data
* The file was seek'ed, which means that @data->dent
* is now invalid. This may also be just the first
* 'ubifs_readdir()' invocation, in which case
* @file->private_data is NULL, and the below code is
* @data->dent is NULL, and the below code is
* basically a no-op.
*/
kfree(file->private_data);
file->private_data = NULL;
kfree(data->dent);
data->dent = NULL;
}
/*
* 'generic_file_llseek()' unconditionally sets @file->f_version to
* zero, and we use this for detecting whether the file was seek'ed.
* 'ubifs_dir_llseek()' sets @data->cookie to zero, and we use this
* for detecting whether the file was seek'ed.
*/
file->f_version = 1;
data->cookie = 1;
/* File positions 0 and 1 correspond to "." and ".." */
if (ctx->pos < 2) {
ubifs_assert(c, !file->private_data);
ubifs_assert(c, !data->dent);
if (!dir_emit_dots(file, ctx)) {
if (encrypted)
fscrypt_fname_free_buffer(&fstr);
@ -641,10 +647,10 @@ static int ubifs_readdir(struct file *file, struct dir_context *ctx)
}
ctx->pos = key_hash_flash(c, &dent->key);
file->private_data = dent;
data->dent = dent;
}
dent = file->private_data;
dent = data->dent;
if (!dent) {
/*
* The directory was seek'ed to and is now readdir'ed.
@ -658,7 +664,7 @@ static int ubifs_readdir(struct file *file, struct dir_context *ctx)
goto out;
}
ctx->pos = key_hash_flash(c, &dent->key);
file->private_data = dent;
data->dent = dent;
}
while (1) {
@ -701,15 +707,15 @@ static int ubifs_readdir(struct file *file, struct dir_context *ctx)
goto out;
}
kfree(file->private_data);
kfree(data->dent);
ctx->pos = key_hash_flash(c, &dent->key);
file->private_data = dent;
data->dent = dent;
cond_resched();
}
out:
kfree(file->private_data);
file->private_data = NULL;
kfree(data->dent);
data->dent = NULL;
if (encrypted)
fscrypt_fname_free_buffer(&fstr);
@ -733,7 +739,10 @@ static int ubifs_readdir(struct file *file, struct dir_context *ctx)
/* Free saved readdir() state when the directory is closed */
static int ubifs_dir_release(struct inode *dir, struct file *file)
{
kfree(file->private_data);
struct ubifs_dir_data *data = file->private_data;
kfree(data->dent);
kfree(data);
file->private_data = NULL;
return 0;
}
@ -1712,6 +1721,24 @@ int ubifs_getattr(struct mnt_idmap *idmap, const struct path *path,
return 0;
}
static int ubifs_dir_open(struct inode *inode, struct file *file)
{
struct ubifs_dir_data *data;
data = kzalloc(sizeof(struct ubifs_dir_data), GFP_KERNEL);
if (!data)
return -ENOMEM;
file->private_data = data;
return 0;
}
static loff_t ubifs_dir_llseek(struct file *file, loff_t offset, int whence)
{
struct ubifs_dir_data *data = file->private_data;
return generic_llseek_cookie(file, offset, whence, &data->cookie);
}
const struct inode_operations ubifs_dir_inode_operations = {
.lookup = ubifs_lookup,
.create = ubifs_create,
@ -1732,7 +1759,8 @@ const struct inode_operations ubifs_dir_inode_operations = {
};
const struct file_operations ubifs_dir_operations = {
.llseek = generic_file_llseek,
.open = ubifs_dir_open,
.llseek = ubifs_dir_llseek,
.release = ubifs_dir_release,
.read = generic_read_dir,
.iterate_shared = ubifs_readdir,